// @(#)VSStack.java   9/2002
// Copyright (c) 1998-2002, Distributed Real-time Computing Lab (DRCL) 
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package drcl.util.queue;

import java.util.Vector;

/**
 * A <i>first-in-last-out</i> queue.
 */
public class VSStack extends VSSimpleQueue
{
  public VSStack()
  { super(); }
  
  public void enqueue(double key_, Object element_, int size_)
  {
    //drcl.Debug.log(this, "enqueue: key=" + key_ + ", element=" + element_ 
    //         + ", size=" + size + ", maxSize=" + maxSize);
    _Element e_ = head;
    _Element new_ = _Element.create(key_, element_, size_);
    // insert before e_.next
    new_.next = e_.next;
    e_.next = new_;
    size += size_; length ++;
    if (new_.next == null) tail = new_;
  }
  
  public boolean enqueueAt(int pos_, double key_, Object element_, int size_)
  {
    _Element e_= head;
    for (int i=0; i<pos_ && e_.next != null; i++, e_ = e_.next);
    
    // insert after e_
    _Element new_ = _Element.create(key_, element_, size_);
    new_.next = e_.next;
    e_.next = new_;
    size += size_; length ++;
    if (new_.next == null) tail = new_;
    return true;
  }
  
  public void merge(Queue that_)
  {
    double[] keys_ = (double[]) that_.keys();
    Element[] elements_ = that_._retrieveAll();
    
    _Element e_ = head;
    
    for (int i=0; i<keys_.length; i++)  {
      int size_ = elements_[i].getSize();
      
      _Element new_ = _Element.create(keys_[i], elements_[i], size_);
    
      // insert after e_
      new_.next = e_.next;
      e_.next = new_;
      size += size_; length ++;
      if (new_.next == null) tail = new_;
      e_ = new_;
    }
  }
  
  
  public void enqueue(Object element_, int size_)
  {
    _Element e_ = head;
    _Element new_ = _Element.create(e_.next == null? 0.0: e_.next.key, element_, size_);
    // insert before e_.next
    new_.next = e_.next;
    e_.next = new_;
    size += size_; length++;
    if (new_.next == null) tail = new_;
  }
  
  
  public Object retrieveBy(double key_)
  {
    for (_Element e_ = head; e_.next != null; e_ = e_.next)
      if (e_.next.key == key_) return e_.next.obj;
    return null;
  }
  
  
  
  public Object[] retrieveAll(double key_)
  {
    Vector v_ = new Vector();
    for (_Element e_ = head; e_.next != null; e_ = e_.next)  
      if (e_.next.key == key_) v_.addElement(e_.next.obj);
    Object[] oo_ = new Object[v_.size()];
    v_.copyInto(oo_);
    return oo_;
  }
  
  
  public boolean containsKey(double key_)
  { 
    for (_Element e_ = head; e_.next != null; e_ = e_.next)
      if (e_.next.key == key_) return true;
    return false;
  }
}
